The cAMP receptor protein (CRP) plays a key role in transcription of catabolite repressible operons as a positive regulatory factor via cAMP dependent DNA (promoter) binding. The proposed research involves an investigation of the role of CRP structure and function for cAMP and DNA binding. CRP has a domain structure in which the amino proximal region is involved in binding cAMP and subunit-subunit interaction while the carboxyl proximal region is involved in DNA binding. Polypeptide fragments and cores have been generated by limited proteolysis of CRP; these will be studied with regard to reconstitution of CRP activity, DNA binding and possible regulatory properties for in vitro lac and gal operon expression. Modification of CRP at the carboxyl terminus by carboxypeptidase will be carried out to determine the role of this region in DNA binding and CRP conformation. Chemical modification studies will be continued to determine effects on CRP structure and function. A temperature sensitive CRP mutant will be purified and characterized in terms of the ts lesion; revertants will be selected for study which show properties different from that of wild type CRP. Using hybridomas monoclonal antibodies will be prepared against CRP fragments. These monospecific antibodies will be used as probes of CRP conformation and function.